Copyright © 2003, 2006 Miklos Tirpak, Juha Heinanen, iptelorg GmbH
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Revision $Revision: 1.4 $ | $Date: 2007/01/08 14:58:38 $ |
The module can be used to determine if a call has appropriate permission to be established. Permission rules are stored in plaintext configuration files similar to hosts.allow and hosts.deny files used by tcpd.
When allow_routing function is called it tries to find a rule that matches selected fields of the message.
SER is a forking proxy and therefore a single message can be sent to different destinations simultaneously. When checking permissions all the destinations must be checked and if one of them fails, the forwarding will fail.
The matching algorithm is as follows, first match wins:
Create a set of pairs of form (From, R-URI of branch 1), (From, R-URI of branch 2), etc.
Routing will be allowed when all pairs match an entry in the allow file.
Otherwise routing will be denied when one of pairs matches an entry in the deny file.
Otherwise, routing will be allowed.
A non-existing permission control file is treated as if it were an empty file. Thus, permission control can be turned off by providing no permission control files.
From header field and Request-URIs are always compared with regular expressions! For the syntax see the sample file: config/permissions.allow.
In addition to call routing it is also possible to check REGISTER messages and decide--based on the configuration files--whether the message should be allowed and the registration accepted or not.
Main purpose of the function is to prevent registration of "prohibited" IP addresses. One example, when a malicious user registers a contact containing IP address of a PSTN gateway, he might be able to bypass authorization checks performed by the SIP proxy. That is undesirable and therefore attempts to register IP address of a PSTN gateway should be rejected. Files config/register.allow and config/register.deny contain an example configuration.
Function for registration checking is called allow_register and the algorithm is very similar to the algorithm described in the section called “Call Routing”. The only difference is in the way how pairs are created.
Instead of From header field the function uses To header field because To header field in REGISTER messages contains the URI of the person being registered. Instead of the Request-URI of branches the function uses Contact header field.
Thus, pairs used in matching will look like this: (To, Contact 1), (To, Contact 2), (To, Contact 3), and so on..
The algorithm of matching is same as described in the section called “Call Routing”.
In addition to call routing and REGISTER it is also possible to check REFER messages and decide--based on the configuration files-- whether or not the message should be accepted for forwarding.
Main purpose of the function is to prevent referring a SIP UA to "prohibited" IP addresses. One example is user sending a REFER request to PSTN gateway trying to refer it to an expensive phone number.
Function for Refer-To checking is called allow_refer_to and the algorithm is very similar to the algorithm described in Section 1.1.1. The only difference is in the way how pairs are created.
Instead of Request-URI the function uses Refer-To header field because Refer-To header field in REFER messages contains the URI to which the UA is being referred to. The algorithm of matching is same as described in Section 1.1.1.
The module can be also used for catching messages coming from or going to specific network elements, for example gateways or peering partners.
Users can register or forward the calls to the address of a gateway resulting unauthorized access to them. Such calls must be catched and dropped, see ipmatch functions for details.
Default allow file used by functions without parameters. If you don't specify full pathname then the directory in which is the main config file is located will be used.
Default value is “permissions.allow”.
Default file containing deny rules. The file is used by functions without parameters. If you don't specify full pathname then the directory in which the main config file is located will be used.
Default value is “permissions.deny”.
Example 2. Set default_deny_file parameter
... modparam("permissions", "default_deny_file", "/etc/permissions.deny") ...
If both of the default file parameters are set to "" the module does not try to load them.
If set then allow_routing functions will check Request-URI of all branches (default). If disabled then only Request-URI of the first branch will be checked.
Do not disable this parameter unless you really know what you are doing.
Default value is 1.
Suffix to be appended to basename to create filename of the allow file when version with one parameter of either allow_routing or allow_register is used.
Including leading dot.
Default value is ".allow".
Suffix to be appended to basename to create filename of the deny file when version with one parameter of either allow_routing or allow_register is used.
Including leading dot.
Default value is ".deny".
Module initialization fails in case of a missing config file if safe_file_load is true.
Default value is 0 (false).
Disables/enables database cache.
Default value is 0 (cache is disabled)
NOTE: ipmatch functions can operate only in cache mode, set db_mode to 1 if you want to use them.
Returns true if all pairs constructed as described in the section called “Call Routing” have appropriate permissions according to the configuration files. This function uses default configuration files specified in default_allow_file and default_deny_file.
Returns true if all pairs constructed as described in the section called “Call Routing” have appropriate permissions according to the configuration files given as parameters.
Meaning of the parameters is as follows:
basename - Basename from which allow and deny filenames will be created by appending contents of allow_suffix and deny_suffix parameters.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
Returns true if all pairs constructed as described in the section called “Call Routing” have appropriate permissions according to the configuration files given as parameters.
Meaning of the parameters is as follows:
allow_file - File containing allow rules.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
deny_file - File containing deny rules.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
The function returns true if all pairs constructed as described in the section called “Registration Permissions” have appropriate permissions according to the configuration files given as parameters.
Meaning of the parameters is as follows:
basename - Basename from which allow and deny filenames will be created by appending contents of allow_suffix and deny_suffix parameters.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
The function returns true if all pairs constructed as described in the section called “Registration Permissions” have appropriate permissions according to the configuration files given as parameters.
Meaning of the parameters is as follows:
allow_file - File containing allow rules.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
deny_file - File containing deny rules.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.
The function returns true if all pairs constructed as described in the section called “Registration Permissions” have appropriate permissions according to the configuration files given as parameters.
Meaning of the parameters is as follows:
basename - Basename from which allow and deny filenames will be created by appending contents of allow_suffix and deny_suffix parameters.
If the parameter doesn't contain full pathname then the function expects the file to be located in the same directory as the main configuration file of the server.